Dynamic two-phase flow behaviors in permeable network integrated with microchannel

Abstract

• Permeable network integrated with microchannel is developed. • Two-phase flow characteristics in such a structure are visually studied. • Liquid saturation increases with increasing gas flow rate. • Position for bubble generation increases with increasing gas flow rate. • Two-phase flow exhibits strong periodicity at low gas flow rates. The performance of a direct methanol fuel cell greatly depends on the two-phase flow behaviors in the anode gas diffusion layer and flow channel. However, complex and opaque nature of gas diffusion layer poses a grand challenge for deep insight into the two-phase flow behaviors. Therefore, a homogeneous permeable network integrated with a microchannel was put forward to simulate the anode gas diffusion layer and microchannel in the present study, by which the dynamic two-phase flow behaviors were visually studied with the help of adaptive image enhancement method. The influence of the position and number of the gas inlet, and the gas and liquid flow rates on the two-phase flow behavior were analyzed. The results showed that the liquid saturation decreased and the number of the position for bubble generation increased with increasing the gas flow rate in case the gas was suppled from only one gas supply orifice. When two gas supply orifices simultaneously supplied the gas, the liquid saturation was between the cases using a single one gas supply orifice. For given liquid and gas flow rates of 0.1 mL/min and 0.5 mL/min, the liquid saturation was about 84%, which was between 83% and 92% for the single-one cases. Besides, the two-phase flow exhibited strong periodicity at low gas flow rates. The obtained results provide a deep understanding of the two-phase flow behaviors in such a simulated structure, helping better design and operation of direct methanol fuel cells.